The present invention relates to improvement technology of a charge pump circuit, and to technology which is effective when applied to a power supply circuit of a nonvolatile memory, for example.
A semiconductor device using a nonvolatile memory is configured by a nonvolatile memory, its peripheral circuit, and others. A nonvolatile memory is provided with a floating gate, a control gate, etc. which are stacked over a substrate. In a semiconductor device using such a nonvolatile memory, various kinds of power supply for operating the nonvolatile memory and its peripheral circuit are generated by an internal power supply voltage generating circuit. Especially, a charge pump circuit is used for a step-up of high voltage.
A charge pump circuit includes a positive voltage step-up circuit and a negative voltage step-up circuit, as described in Patent Document 1 (paragraphs 0038-0052). According to Patent Document 1, capacitor structure of a charge pump circuit of a flash memory is configured by a capacitor C1 formed by an insulating film sandwiched between a first gate FG in the same layer as a floating gate and a second gate SG in the same layer as a control gate of a nonvolatile memory cell, and a capacitor C2 formed by an insulating film sandwiched between the first gate FG and a well region nwell. The second gate SG and the well region nwell are formed at the same potential, and the capacitor C1 and the capacitor C2 are coupled in parallel. The capacitor C1 and the capacitor C2 are stacked in a tandem structure.
(Patent Document Japanese Patent Laid-open No. 2001-085633